Process for producing conjugated diolefin polymer with reduced cold flow

ABSTRACT

A process for producing a homopolymer or copolymer of a conjugated diolefin by polymerizing a conjugated diolefin alone or copolymerizing a conjugated diolefin with a vinyl aromatic hydrocarbon in the presence of a lithium-type initiator in a hydrocarbon solvent, characterized in that the quantity of said initiator required for the polymerization is divided into two portions, A and B, in a molar ratio of A : B 1 : 3 to 15, and said portion A is added at the outset to initiate the polymerization, and when the conversion to polymer has reached 20 to 60 percent by weight said portion B is added to the polymerization system to carry out the polymerization until it is substantially completed. The polymer obtained by the present process retains the desirable properties which a conventional conjugated diolefin polymer has, and is, in addition, characterized by reduced cold flow.

United States Patent 11 1 3,669,943

Komatsu et a]. June 13, 1972 [54] PROCESS FOR PRODUCING 3,119,800 1/1964 Moss et al ..260/94.2 CONJUGATED DIOLEFIN POLYMER 3,318,862 5/1967 Hinton ..260/94.2 WITH REDUCED COLD FLOW 3,350,380 /1967 Strobe] ..260/94.2 3,393,182 7/1968 Trepka ..260/94.2

[72] Inventors: Koei Komatsu, Yokohama; Eitaro Okuya,

Yokkaichi; Katsuyoshi Tomioka, FOREIGN PATENTS OR APPLICATIONS Ykhamai Mass Sakai *kaichii 943,939 12/1963 Great Britain ..260/94.2

Shigeki Hayashi, Yokkaichi; Hidetoshi YaSunaga Yokkaichi; Akita Kogure 339,243 12/1930 Great Britain... ..260/94.2

Tokyo, all of Japan Primary Examiner-James A. Seidleck [73] Assignees Japan Synthetic Rubber Co., Ltd., Chuo- Att0rney-Waters, Roditi, Schwartz& Nissen ku, Tokyo, Japan [22] Filed: May 28,1970

[21] AppliNo; 41,619

[5 7] ABSTRACT A process for producing a homopolymer or copolymer of a conjugated diolefin by polymerizing a conjugated diolefin alone or copolymerizing a conjugated diolefin with a vinyl aro- Foreign Application Priority Data matic hydrocarbon in the presence of a lithium-type initiator in a hydrocarbon solvent, characterized in that the quantity of May 31, 1969 Japan ..44/41719 said initiator required for the polymerization is divided into two portions, A and B, in a molar ratio ofA B l 3 to 15,

[52] 6 4 and said portion A is added at the outset to initiate the [51] Int Cl d 1/32 19/02; l/z's polymerization, and when the conversion to polymer has [58] Fie'ld 260/831] 94 2 M 2 T 82 1 reached 20 to 60 percent by weight said portion B is added to 260/ 7 the polymerization system to carry out the polymerization until it is substantially completed. The polymer obtained by the present process retains the desirable properties which a [56] References Clted conventional conjugated diolefin polymer has, and is, in addi- UNITED STATES PATENTS tion, characterized by reduced cold flow.

3,592,799 7/1971 Rouzier ..260/94.2 M 13 Claims, No Drawings PROCESS FOR PRODUCING CONJUGATED DIOLEFIN POLYMER WITH REDUCED COLD FLOW This invention relates to a process for producing a homopolymer or copolymer of a conjugated diolefin having reduced cold flow. More particularly, this invention relates to a process for producing a rubber-like polymer with reduced cold flow by polymerizing a conjugated diolefin alone or in admixture with a vinyl aromatic hydrocarbon in the presence of a lithium-type initiator.

The polymerization of conjugated diolefins alone or copolymerization thereof with vinyl aromatic hydrocarbons by use of a lithium-type initiator has recently become industrially important, and commercial products, such as Cariflex," Diene, Duradene, Solprene and the like, are being produced and marketed.

These polymers generally possess excellent physical properties in addition to their low ash content and non-staining characteristics, and they have grown to occupy an important position in the synthetic rubber field, sharing the market with such polymers as cis-1,4-polybutadiene and cis-l,4- polyisoprene which are produced with a catalyst containing a transition metal.

However, when a monomer is contacted at a time with the entire quantity of a lithium-type initiator, the resulting polymer has a narrow molecular weight distribution which imparts to the polymer molecules a slipping tendency that will cause certain difficult problems concerning packaging, transportation and storage of the polymer.

Thus, the above-mentioned polymer in the unvulcanized state generally has a tendency to flow at about room temperature (i.e., cold flow). As a result, in case the packed products have been piled up for storage or transportation, a part of the package is liable to rupture, and once ruptured the rubber flows out of the package to become contaminated or the packages of rubber will stick together to cause a handling difficultyl Moreover, when the compounded stock of the polymer is shaped by extrusion or calendering, the resulting shaped articles will be deformed later. This is a fault of said polymer in practice.

Heretofore, in order to obtain a conjugated diolefin polymer with reduced cold flow, an inhibiting agent has specially been added.

As a result of extensive research, the present inventors have found that the above-mentioned object may be achieved without resorting to the addition of said inhibiting agent, by selecting a suitable method of adding the lithium-type initiator.

An object of the present invention is to provide a conjugated diolefin polymer with reduced cold flow.

Another object of the invention is to provide a novel process for producing such a polymer.

Other objects and effects of the invention will be apparent to those skilled in the art from the following description.

According to the present invention, there is provided a process for producing a homopolymer or a copolymer of conjugated diolefin by polymerizing a conjugated diolefin alone or in admixture with a vinyl aromatic hydrocarbon in the presence of a lithium-type initiator in a hydrocarbon solvent, characterized in that the quantity of said initiator required for the polymerization is divided into two portions, A and B, in a' molar ratio of A B l 3 to 15, and at first the portion A of the lithium-type initiator is added to the polymerization system to initiate the polymerization, and when the conversion reaches to 60 percent by weight, the portion B of the lithium-type initiator is added to said system to effect polymerization until it is substantially completed.

As the conjugated diolefin used in the present invention, the preferred are 1,3-butadiene, isoprene, and piperylene.

Styrene, divinylbenzene, a-methylstyrene, B-methylstyrene, vinyltoluene, l-vinylnaphthalene, and 2-vinylnaphthalene may be used as the vinyl aromatic hydrocarbon, styrene being most preferable.

Of the above-mentioned monomers, the most preferable monomers or combinations of monomers are butadiene, isoprene, butadiene-styrene, isoprene-styrene, butadieneisoprene, and butadiene-isoprene-styrene.

As a hydrocarbon solvent, there may be used an aliphatic hydrocarbon, a cycloaliphatic hydrocarbon, and an aromatic hydrocarbon that are liquid under the polymerization conditions. Preferable hydrocarbon solvents are propane, n-pentane, isopentane, n-hexane, n-heptane, n-octane, isooctane, ndecane, cyclopentane, cyclohexane, methylcyclopentane, ethylcyclohexane, benzene, toluene, xylene, etc. The hydrocarbon solvent is preferably used in an amount of l to 20 parts by weight per part by weight of the monomer.

The lithium-type initiators used in the present process are metallic lithium: alkyllithiums, such as ethyllithium, propyllithium, n-butyllithium, sec.-butyllithium, tert-butyllithium and isobutyllithium; aryllithiums, such as phenyllithium and tolyllithium; alkenyllithiums, such as vinyllithium and propenyllithium; alkylenedilithiums, such as tetramethylenedilithium and hexamethylenedilithium; arylenedilithiums, such as 1,3-dilithiobenzene and 1,4- dilithiobenzene; 1,3,5-trilithiocyclohexane; 1,2 ,5- trilithionaphthalene; l ,3,5,8-tetralithiodecane; l,2,3,5- tetralithio-4-hexylanthracene, etc. These lithium-type initiators are added to the polymerization system in the form of a suspension or a solution in a hydrocarbon solvent which is preferably the same as the polymerization solvent.

Mainly, in the case of copolymerization of butadiene and styrene or the like, additives such as a so-called randomizer and a molecular weight regulator may suitably be used in combination with the above-mentioned lithium-type initiators.

As the main randomizers used in combination with the lithiurn compounds, the following may be illustrated:

(I) Ethers, thioethers, or tertiary amines [Japanese Pat. No. 290,238 (Publication No. 15,386/61 )1.

(Belgian Pat. No. 663, 879);

(III) Anionic surface active agents having a hydrophilic group represented by SO M or OSO M (M Na, K, etc.) (Japanese Pat. Publication No. 12,146/71 (IV) (R N) -,P or (R N) P= 0 (Japanese Patent Publication No. 22,399/70 and Japanese Patent Publication No. 26,630/68).

Other known randomizers and molecular weight regulators than those mentioned above may be used in the present process in combination with said polymerization initiators.

As the polymerization temperature, there is ordinarily used a temperature of 10 to 150 C., and preferably 20 to C. The polymerization pressure may be any pressure that is suffrcient to keep the reaction mixture in a liquid state, and ordinarily, a pressure of about 1 to 5 atm., is used, though the reaction may be conducted under higher or lower pressures in special cases.

The polymerization is preferably conducted under an atmosphere of an inert gas, such as nitrogen or argon.

The polymerization is effected by contacting a conjugated EXAMPLE 1 diolefin or a mixture of a conjugated diolefin and a vinyl aromatic hydrocarbon with a lithium-type initiator in a hydrocar- Table 1 bon solvent. The method of adding the lithium-type initiatoris Run 1 2 3 4 as follows: The quantity of lithium-type initiator is divided into 5 two portionsaA and B in a molar ratio of A z B 1 I 3 to Monomer Butadiene Butadiene lsoprene lsoprene and the A portion of the lithium-type initiator is at first added Ratio of divided to the polymerization system. The optimum concentration of C i t d t 1 1:5 110 the active lithium at this stage is 0.001 to 1.0 millimole per se ma 0A8 0A8 0A8 048 100 gr. of monomer. In the presence of the A portion of the 10 Firstly added (mhm) 0.48 0.08 0.48 0.08 lithium-type initiator, polymerization is effected until the con Secondly added version reaches to 60 percent by weight, when the B por- (mhm) 0A0 Conversion to polymer tion of the lithium-type initiator is added. The optimum con- 3 5 35 centration of the active lithium of the B portion is 0.01 to l0 15 Reaction temperature 0 millimoles per 100 gr. of monomer. The B portion of the lithi- 40 40 4 um-type initiator may be further divided into two or more por- 53 3 232 533x223 300 300 300 300 tions and added portionwise. After the addition of the B por- 97 100 95 97 tion at the latter stage, the polymerization is allowed to cold flow (nigh/mi) proceed until the substantial completion of the reaction, or- 20 dinarily until a conversion of more than 80 percent is reached. Note: 5 00 Parts y ght f z n a l nt a us d p r 100 Said A and B portions may be added to the reaction system 2 v s if z fg f either continuously or batchwise. ln the present process, the )m m mm es per o monomer molar ratio of the A portion to the B portion and the conver- Butadiene and isoprene were polymerized under the condision range in which the B portion should be added, are limited tions as shown in Table 1. Run Nos. 1 and 3 are comparative to the ranges given above, because when the conversion at mm 1 s whi h are not included within the 50 e f the in which the B portion should be added is more than 60 percent e e c p o vention. The procedure of polymerization was as follows: The or when the molar ratio of the A portion to the B portion is l dried and purified solvent and the monomer were introduced less than 3, there cannot be obtained a polymer having improved cold flow Further when the conversion at which the B g l g i vessel z i g 't ar as, n tevsse was eate portion should be added is less than 20 percent or when the an 6 gon g a an e f l to t e molar ratio of the A portion to the B portion is l more than reacuon temperature' Then a Sm quantity 0 a so i l 5 the CO1 d flow can be improved but there carmm be butyllith ium was added to the vessel to remove any impur ty taiiied a polymer having various properties required for cong i m the 'g ifgg a preddetgrmlged quanmy o t ecatalyst,i.e.,nuty i ium,wasa de tot esystem to ventional rubbers, for example, tensile strength, processability initiate polymerization. In Run 2 and 4 the quantity of and the like. The temperature and pressure at which the A and the catalyst was divided in a molar ratio of 1 5 and one sixth B portions are added are preferably near the polymerization of the total quantity was firstly added initiate the temperature and pressure, though not critical. When a ranpolymerization and tha remaining five simhs was added when domizer or a mokcular weight 9 F it y the conversion had reached 40 percent, to continue the it? 3.:s;; i.z"sttiziizzszi; ii siz'siz zzitx e i i or a pre etermine perio a Sin amount 0 isopropy a tf x i f 9 l ii Started 1P9 fi g s cohol was added to the system to terminate the polymerizaiso r0 1 co 0 wit stirrin to coa u ate t e o mer, an cess of the lithium-type initiator. The excess lithium-type inff polymer was driegd undflgvacuum hours itiator is not included in the above-mentioned amount of the A C. and B Portions The values of cold flow of the polymers were as shown in w f the macho" been substantially compleedi an the last line in Table 1. By comparing the values of Run Nos. 1 anti-oxidant and a terminator, such as water, alcohols or the and 3 with those of Run NOS 2 and 4, the advantage of using like, are added in a conventional manner to terminate the 50 the catalyst, divided ponionsis evidem polymerization, and the resulting polymer is separated, EXAMPLE 2 it i dnfid 'i u x e P s a b f The copolymerization of butadiene with styrene was carried 6 P y 0 3 P Sen m y e e out under the conditions as shown in Table 2. Run Nos. 5 and fected not only batchwise but also continuously with satisfac- 6 were Shown as comparative examples, which are not eluded within the scope of the invention. The procedure of Present invemkfn is P y explained below by polymerization was as follows: The dried and purified solvent refemllg to l followmg examples l" however, are y and the monomer were introduced into a polymerization vesfllfh '-l 3 :1 P ts) y oflllmltatlcnk d b so] which had been thoroughly dried and flushed with argon e co 0W give" e eXamP e5 was 6 emme 3' as, and the vessel was heated to the reaction tern erature. g the Polymer through aone'foul'th inch Orifice l'hen a small quantity of a solution of n-butyllith ium was at a pressure of 3.5 lbs/hi In order to obtain the steady state, dd d t th v ssel to remove any impurity present in the P y was alloweq to be extruded 10 -i afi er system. Subsequently, a predetermined quantity of potassium which the rate of extrusion was measured and expressed in d d lb lf t (as a benzene hm f 105 milli rams er minute.

Thge Mocfne ML d 105 C b mole/l )as a randomizer and a predetermined quantity of n y vlscoslty 1+4) measure at 3 butyllithium as the catalyst were added to initiate polymerizameans of Goodrich Mooney viscosirrieter. i

TABLE 2 Run number 5 6 7 8 9 10 11 12 13 s ilvgnu n u fi p g ag z pi a g s g s; y ex u g ptguai; H pibal'ig He t ei ie an ornzer m m. ,0 Ratio of divided catalyst 1:0 1:2 1:3 1:4 l:5 1:7 1:0 1:10 1:12 Catalyst used (total) (n1lini.) 0.50 0. 60 0.60 0.60 0.62 0.67 0.60 l). 0. 70 Firstly added (m1nn.).-. 0.50 0. 20 0.15 0.12 0.11 0. 0s 0. 06 0.064 0.054 Secondly iiddod (mhmJ. r. 0. 40 0.22 0.12 0. 51 0.581 0. 14 0.33 O. 646 Conversion to polymer (port-0111).. 0 40 20-52 40 50 20-40 34 30 lhlrilly added (1iihi1i.) 0.23 0.36 0.40 0.306

TABLE 2 -Conlinued Run number 5 6 7 8 J 10 11 12 13 Conversion to polymer (percent) 55 52 40 54 Reaction temperature C.) 50 50 45 55 55 55 65 50 55 Reaction period (min.) 130 200 220 280 90 210 160 320 300 Ultimate conversion (percent) 80 95 95 96 100 100 93 98 90 Mooney viscosity 52 55 48 51 35 48 51 40 43 Cold flow (mgr./min.) 9. 7. 1. 5 2. 4 0. 6 0. 4 2.6 1 3 3 0 Nora-3,000 gr. of the solvent was used per 600 gr. of monomer (150 gr. of styrene and 450 gr. of butadiene).

In Run No. 5, the catalyst was added not in portions but as a whole at the outset. In Run Nos. 6, 9, and 13, a portion of the catalyst was added at the outset of polymerization and the remainder was added when the conversion reached 30 to 50 percent. In Run Nos. 7 and 12, one of three portions of the catalyst was added at the outset, and the remaining two portions were added at a conversion of 34 to 40 percent, and at a conversion of 54 to 55 percent. In Run Nos. 8 and l l, the first portion of the catalyst was added at the outset, the second portion was added continuously while the conversion increases from 20 to 52 percent or from 20 to 40 percent, respectively, and the remainder was added at a conversion of 52 or 40 percent, respectively.

After the polymerization had been carried out for a predetermined period, a small amount of isopropyl alcohol was added to terminate the polymerization. Two parts by weight of an antioxidant was added for 100 parts by weight of the polymer in solution, and then the solvent was removed by blowing steam into the solution with stirring, to obtain the polymer which was then formed into a sheet on a mixing mill and dried.

Run Nos. 1 and 3 in Example 1 and Run Nos. 5 and 6 in Example 2 are comparative examples for comparison. By comparing these comparative examples with Examples of the present process, it is evident that the cold flow characteristic of the polymer obtained by the present process is remarkably improved.

What we claim is:

1. A process for producing a homopolymer or a copolymer of conjugated diolefin by polymerizing a conjugated diolefin alone or in admixture with a vinyl aromatic hydrocarbon in the presence of an initiator selected from the group consisting of metallic lithium and an organic lithium compound in a hydrocarbon solvent, characterized in that the quantity of said initiator required for the polymerization is divided into two portions, A and B, in a molar ratio of A B 1 3 to 15, and the A portion of the initiator is added to the polymerization system at the outset to initiate the polymerization, and when the conversion reaches 20 to 60% by weight, the B portion of the initiator is added to said system without deactivating the active species initiated by the A portion of initiator, and thereafter, the polymerization is carried out until it is substantially completed, the concentration of active lithium of the A portion being 0.001 to 1.0 millimole per gr. of the monomer and the concentration of active lithium of the B portion being 0.01 to 10 millimoles per 100 gr. of the monomer.

2. A process according to claim 1, wherein the molar ratio of the A portion to the B portion iw is l 3 to 12.

3. A process according to claim 1, wherein the polymerization temperature is from 10 to C.

4. A process according to claim 1, wherein the polymerization pressure is from 1 to 5 atms.

5. A process according to claim 1, wherein the polymerization is carried out under an atmosphere of an inert gas.

6. A process according to claim 1, wherein the conjugated diolefin is 1,3-butadiene, isoprene, or piperylene.

7. A process according to claim 1, wherein the vinyl aromatic hydrocarbon is styrene, divinylbenzene, a-methylstyrene, B-methylstyrene, vinyltoluene, l-vinylnaphthalene, or Z-vinyInaphthalene.

8. A process according to claim 1, wherein butadiene or isoprene is homopolymerized.

9. A process according to claim 1, wherein butadiene or isoprene is copolymerized with styrene.

10. A process according to claim 1, wherein butadiene and isoprene are copolymerized, or butadiene, isoprene and styrene are copolymerized.

11. A process according to claim 1, wherein the hydrocarbon solvent is propane, n-pentane, isopentane, n-hexane, nheptane, n-octane, isooctane, n-decane, cyclopentane,

cyclohexane, methylcyclopentane, ethylcyclohexane, benzene, toluene, or xylene.

12. A process according to claim 1, wherein the initiator is metallic lithium, an alkyllithium, an aryllithium, an alkenyllithium, an alkylenedilithium, an arylene-dilithium, 1,3,5- trilithiocyclohexane, 1,2,5-trilithionaphthalene, 1,3,5,8- tetralithiodecane, or 1,2,3,5-tetralithio-4-hexylanthracene.

13. A process according to claim 1, wherein the initiator is n-butyllithium. 

2. A process according to claim 1, wherein the molar ratio of the A portion to the B portion iw is 1 : 3 to
 12. 3. A process according to claim 1, wherein the polymerization temperature is from 10* to 150* C.
 4. A process according to claim 1, wherein the polymerization pressure is from 1 to 5 atms.
 5. A process according to claim 1, wherein the polymerization is carried out under an atmosphere of an inert gas.
 6. A process according to claim 1, wherein the conjugated diolefin is 1,3-butadiene, isoprene, or piperylene.
 7. A process according to claim 1, wherein the vinyl aromatic hydrocarbon is styrene, divinylbenzene, Alpha -methylstyrene, Beta -methylstyrene, vinyltoluene, 1-vinylnaphthalene, or 2-vinylnaphthalene.
 8. A process according to claim 1, wherein butadiene or isoprene is homopolymerized.
 9. A process according to claim 1, wherein butadiene or isoprene is copolymerized with styrene.
 10. A process according to claim 1, wherein butadiene and isoprene are copolymerized, or butadiene, isoprene and styrene are copolymerized.
 11. A process according to claim 1, wherein the hydrocarbon solvent is propane, n-pentane, isopentane, n-hexane, n-heptane, n-octane, isooctane, n-decane, cyclopentane, cyclohexane, methylcyclopentane, ethylcyclohexane, benzene, toluene, or xylene.
 12. A process according to claim 1, wherein the initiator is metallic lithium, an alkyllithium, an aryllithium, an alkenyllithium, an alkylenedilithium, an arylene-dilithium, 1,3, 5-trilithiocyclohexane, 1,2,5-trilithionaphthalene, 1,3,5,8-tetralithiodecane, or 1,2,3,5-tetralithio-4-hexylanthracene.
 13. A process according to claim 1, wherein the initiator is n-butyllithium. 